Funding for this research was provided by:
Bộ Giáo dục và Ðào tạo (637/Q-D-BGD-DT)
Received: 7 September 2020
Accepted: 27 January 2021
First Online: 8 March 2021
Ethics approval and consent to participate
: All procedures involving in this study were conducted in compliance to the recommendations of the <i>Guide for the Care and Use of Agricultural Animals in Research and Teaching (2010)</i> [CitationRef removed] <i>since</i> North Vietnam does not impose ethics on the use of local animals for research [CitationRef removed].
: Not applicable.
: The authors declare that they have no competing interests.